Transmission disconnection by wheel rotation for walk-behind machine

ABSTRACT

A walk-behind machine includes a clutch having a driving state where a motor drives wheels to rotate and an unlocked state where the wheels freely rotate relative to the motor. The clutch includes a movable member and a driving member. The movable member is capable of moving between a locked position where the clutch is in the driving state and an unlocked position where the clutch is in the unlocked state. The driving member transfers power to the wheels by means of friction. When the clutch is in the driving state, the motor drives the wheels to rotate in a first direction, when the motor stops rotating, the wheels rotate in a second direction opposite to the first direction and can drive the driving member to move by frictional force so that the driving member pushes the movable member to move from the locked position to the unlocked position.

RELATED APPLICATION INFORMATION

This application is a continuation of U.S. patent application Ser. No.16/371,267 filed Apr. 1, 2019, which claims the benefit of ChinesePatent Application No. 201611205394.X, filed on Dec. 23, 2016, andChinese Patent Application No. 201711093658.1, filed on Nov. 8, 2017,each of which is incorporated herein by reference in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates to a walk-behind machine.

BACKGROUND

Lawn mowers, snow throwers, etc. are typical walk-behind machines. Awalk-behind machine includes a motor, a plurality of wheels, and atransmission mechanism. The motor drives the wheels to rotate throughthe transmission mechanism so that the walk-behind machine movesrelative to the ground.

The walk-behind machine requires the right wheel and the left wheel torotate at different speeds during steering. The walk-behind machine isprovided with a clutch to enable the right wheel and the left wheel torotate asynchronously. Generally, the rotation speed of a wheel isgreater than the other wheel's. The clutch is also called a differentialdevice. For the typical walk-behind machine with that clutch, when themotor shaft stops rotating, the machine can be pushed forward to makethe wheels continue to rotate forward, and the clutch can cut off thetransmission between the wheels and the motor shaft. When the motorstops rotating and the machine is pulled backward to rotate the wheelbackward, the clutch cannot disconnect the transmission between thewheels and the motor shaft, and the wheels will drive the motor shaft torotate. At this point where the differential device is in a drivingstate, a large force is required to pull the walk-behind machine to movebackward, which is known as the “lock-up” phenomenon. After the motorstops rotating, in order to disconnect the transmission between thewheels and the motor shaft and in order to make the differential deviceenter into an unlocked state, the machine needs to be pushed forward tounlock the differential device, then the wheels can rotate freelyrelative to the motor shaft. Pulling the walk-behind machine backwardcannot make the machine “unlocked,” which brings great inconvenience tousers.

After the motor stops and when the machine is pushed or is pulled, thewheels will rotate and drive the motor shaft to rotate through thetransmission mechanism. In that condition, a great force is required topush or pull the machine to move.

SUMMARY

In one aspect of the disclosure, a walk-behind machine, includes achassis, a handle, wheels, a first motor, a working element, a secondmotor, and a transmission mechanism. The handle is connected to thechassis. The wheels are for supporting the chassis and can rotaterelative to the chassis. The first motor is mounted to the chassis, forproviding a driving force to rotate the wheels. The working elementmoves relative to the chassis to implement the machine's function. Thesecond motor is for driving the working element to move. Thetransmission mechanism connects the first motor with the wheels andincludes a clutch for realizing one-way transmission between the firstmotor and the wheels, wherein the clutch has a driving state where thefirst motor drives the wheels to rotate and an unlocked state where thewheels freely rotate relative to the first motor. The clutch includes amovable member and a driving member. The movable member is capable ofmoving between a locked position and an unlocked position. The drivingmember transfers power with the wheels by means of friction. When themovable member is in the locked position, the clutch is in the drivingstate where the first motor is capable of driving the wheels to rotatein a first direction. When the movable member is in the unlockedposition the clutch is in the unlocked state. When the first motor stopsrotating, the wheels rotate in a second direction opposite to the firstdirection, and can drive the driving member to move so that the drivingmember pushes the movable member to move from the locked position to theunlocked position.

In one or more examples, the first motor includes a motor shaft foroutputting a driving force. The clutch includes a transmission shaft, afixing member and an outer ring member. The transmission shaft isconnected to the motor shaft and is driven by the motor shaft to rotate.The fixing member is coupled to the transmission shaft or is a part ofthe transmission shaft and forms a driving surface capable of drivingthe movable member. The outer ring member is sleeved on the transmissionshaft, is connected to the wheels to drive the wheels to rotate andforms a mounting groove. The movable member is located between the wallof the mounting groove and the driving surface.

In one or more examples, the wall of the mounting groove is an annularsurface, and the movable member is a pin.

In one or more examples, the driving member includes a plurality ofdriving portions, and the driving portions get into the mounting grooveand are capable of contacting the movable member to push the movablemember to move.

In one or more examples, the clutch includes a plurality of movablemembers and the number of the movable members is the same as the numberof driving portions. The driving portions and the movable members arealternatively arranged.

In one or more examples, the fixing member forms a plurality of drivingsurfaces and the number of the driving surfaces is the same as thenumber of movable members, the driving surfaces are in one-to-onecorrespondence with the movable members.

In one or more examples, the frictional force between the wheels and thedriving member is greater than the frictional force between the fixingmember and the movable member when the movable member is in the lockedposition.

In one or more examples, the wheels form a first wheel gear or a firstwheel gear is mounted on the wheels. The walk-behind machine furtherincludes a first transmission gear meshing with the first wheel gear anddriven by the transmission shaft to drive the wheel to rotate. When themotor shaft actively rotates, the transmission shaft drives the firsttransmission gear to rotate so as to rotate the wheels and the wheelsexert a force, whose direction is opposite to the rotation direction ofthe first transmission gear, to the driving member.

In one or more examples, the wheels form a second wheel gear or a secondwheel gear is mounted on the wheels. The walk-behind machine furtherincludes a second transmission gear meshing with the second wheel gear.When the wheels rotate, the first transmission gear and the secondtransmission gear rotate in opposite directions and the secondtransmission gear exerts a force, whose direction is opposite to therotation direction of the first transmission gear, to the drivingmember.

In one or more examples, the walk-behind machine further includes afriction plate disposed between the second transmission gear and thedriving member and realizing the friction transmission between thesecond transmission gear and the driving member.

In one or more examples, the clutch includes a magnet exerting amagnetic attractive force to the movable member.

In one or more examples, the clutch includes a plurality of the movablemembers and the magnets, whose number is equivalent to the number of themovable members. The transmission shaft rotates about a central axis, inthe direction of which magnets exert a magnetic attractive force to themovable members of the central axis.

In one or more examples, the magnets are fixed to the outer ring memberand are evenly distributed in the circumferential direction of thecentral axis.

In one or more examples, the magnet is annular and surrounds thetransmission shaft.

A walk-behind machine, includes a chassis, a working element, a handle,wheels, a motor and a clutch. The working element moves relative to thechassis to implement the machine's function. The handle is connected tothe chassis. The wheels are for supporting the chassis and can rotaterelative to the chassis. The motor is capable of providing a drivingforce for rotating the wheels and includes a motor shaft for outputtingthe driving force. The clutch is capable of one-way transmitting betweenthe motor shaft and the wheels. The clutch has a driving state where themotor shaft drives the wheels to rotate and an unlocked state where thewheels freely rotate relative to the motor shaft. The clutch includes amovable member and a driving member. The movable member is capable ofmoving between a locked position and an unlocked position. The drivingmember could be driven by the wheels. When the movable member is in thelocked position the clutch is in the driving state where the motor shaftdrives the wheels to rotate in a first direction. When the movablemember is in the unlocked position the clutch is in the unlocked state.When the motor shaft stops rotating, the wheels rotate in a seconddirection opposite to the first direction and can drive the drivingmember to move so that the driving member pushes the movable member tomove from the locked position to the unlocked position.

In one or more examples, the wheels drive the driving member byfriction.

In one or more examples, the clutch includes a transmission shaft, afixing member and an outer ring member. The transmission shaft iscoupled to the motor shaft and is driven to rotate by the motor shaft.The fixing member is coupled to the transmission shaft or is a part ofthe transmission shaft and forms a driving surface capable of drivingthe movable member. The outer ring member is sleeved on the transmissionshaft and is connected to the wheels to drive the wheels to rotate. Theouter ring member forms a mounting groove between the wall of which andthe driving surface the movable member is located.

In one or more examples, the wall of the mounting groove is an annularsurface, and the movable member is a pin.

In one or more examples, the driving member includes a plurality ofdriving portions, and the driving portions get into the mounting grooveand are capable of contacting the movable member to push the movablemember to move.

In one or more examples, the clutch includes a plurality of movablemembers and the number of the movable members is equivalent to thenumber of driving portions. The driving portions and the movable membersare alternatively arranged.

In one or more examples, the fixing member forms a plurality of drivingsurfaces and the number of the driving surfaces is the same as thenumber of movable members, the driving surfaces are in one-to-onecorrespondence with the movable members.

In one or more examples, the wheels form a first wheel gear or a firstwheel gear is mounted on the wheels, and the walk-behind machine furtherincludes a first transmission gear meshing with the first wheel gear anddriven by the transmission shaft to drive the wheel to rotate. When themotor shaft actively rotates, the transmission shaft drives the firsttransmission gear to rotate, thereby driving the wheels to rotate andthe wheels exert a force, whose direction is opposite to the rotationdirection of the first transmission gear, to the driving member.

In one or more examples, the wheels form a second wheel gear or a secondwheel gear is mounted on the wheels, and the walk-behind machine furtherincludes a second transmission gear meshing with the second wheel gear.When the wheels rotate, the first transmission gear and the secondtransmission gear rotate in opposite directions and the secondtransmission gear exerts a force whose direction is opposite to therotation direction of the first transmission gear to the driving member.

In one or more examples, the walk-behind machine further includes afriction plate disposed between the second transmission gear and thedriving member and realizing the friction transmission between thesecond transmission gear and the driving member.

In one or more examples, the walk-behind machine has a self-propelledforward-moving mode in which the motor drives the wheels to rotate inthe first direction and a self-propelled backward-moving mode. When themotor is turned off, the walk-behind machine is out of theself-propelled forward-moving mode and the walk-behind machine is pushedforward to make the wheels rotate in the first direction, the wheelsdrive the movable member to move from the locked position to theunlocked position and the clutch turns into the unlocked state. When thewalk-behind machine is in the self-propelled backward-moving mode, themotor drives the wheels to rotate in the second direction opposite tothe first direction. When the motor is turned off, the walk-behindmachine is out of the self-propelled backward-moving mode and thewalk-behind machine is pushed to make the wheels rotate in the seconddirection, the wheels drive the movable member to move from the lockedposition to the unlocked position and the clutch into the unlockedstate.

In one or more examples, when the motor is turned off, the walk-behindmachine is out of the self-propelled forward-moving mode and thewalk-behind machine is pushed backward to make the wheels rotate in thesecond direction, the wheels drive the movable member to move from thelocked position to the unlocked position and the clutch turns into theunlocked state. When the motor is turned off, the walk-behind machine isout of the self-propelled backward-moving mode and the walk-behindmachine is pushed forward to make the wheels rotate in the firstdirection, the wheels drive the movable member to move from the lockedposition to the unlocked position and the clutch turns into the unlockedstate.

In one or more examples, the walk-behind machine has a self-propelledforward-moving mode in which the motor drives the wheels to rotate inthe first direction and a self-propelled backward-moving mode in whichthe motor drives the wheels to rotate in the second direction oppositeto the first direction. When the motor is turned off and the walk-behindmachine is pushed to drive the wheels to turn at an angle in anydirection, the wheels drive the movable member to move from the lockedposition to the unlocked position and the clutch turns into the unlockedstate.

In one or more examples, the walk-behind machine further includes atransmission mechanism connecting the motor shaft and the wheels,wherein the transmission mechanism includes the clutch and a gearboxconnecting the motor shaft and the clutch.

In one or more examples, the clutch includes a magnet exerting amagnetic attractive force to the movable member.

In one or more examples, the clutch includes a plurality of the movablemembers and the magnets, whose number is the same as the number ofmagnets and the transmission shaft rotates about a central axis, in thedirection of which magnets exert a magnetic attractive force to themovable members of the central axis.

In one or more examples, the magnets are fixed to the outer ring memberand are evenly distributed in the circumferential direction of thecentral axis.

In one or more examples, the magnet is annular and surrounds thetransmission shaft.

In one or more examples, the working element is driven to move by themotor.

In one or more examples, the walk-behind machine further includes asecond motor for driving the working element to move.

A walk-behind machine, including a chassis, a handle, wheels, a motor,and a transmission mechanism. The handle is connected to the chassis.The wheels are for supporting the chassis and capable of rotatingrelative to the chassis. The motor is capable of providing a drivingforce for rotating the wheels. The transmission mechanism connects themotor with the wheels and includes a clutch for realizing one-waytransmission between the motor and the wheels. The clutch has a drivingstate where the motor drives the wheels to rotate and an unlocked statewhere the wheels freely rotate relative to the motor. The clutchincludes a movable member capable of moving between a locked positionand an unlocked position. When the movable member is in the lockedposition the clutch is in the driving state where the motor activelyrotates to drive the wheels to rotate. When the movable member is in theunlocked position the clutch is in the unlocked state. When the motorstops rotating, the wheels rotate at an angle in any direction and drivethe movable member to move from the locked position to the unlockedposition.

In one or more examples, the clutch further includes a driving member.When the clutch is in the driving state, the motor can drive the wheelsto rotate in a first direction. When the motor stops rotating, thewheels rotate in a second direction opposite to the first direction, andcan drive the driving member to move so that the driving member pushesthe movable member to move from the locked position to the unlockedposition.

In one or more examples, the wheels can drive the driving member to moveby friction force.

In one or more examples, the motor includes a motor shaft for outputtinga driving force. The clutch includes a transmission shaft, a fixingmember and an outer ring member. The transmission shaft is connected tothe motor shaft and is driven by the motor shaft to rotate. The fixingmember is coupled to the transmission shaft or is a part of thetransmission shaft and forms a driving surface capable of driving themovable member. The outer ring member is sleeved on the transmissionshaft, is connected to the wheels to drive the wheel to rotate and formsa mounting groove. The movable member is located between the wall of themounting groove and the driving surface.

In one or more examples, the wall of the mounting groove is an annularsurface, and the movable member is a pin.

In one or more examples, the wheels form a first wheel gear or a firstwheel gear is mounted on the wheels. The walk-behind machine furtherincludes a first transmission gear meshing with the first wheel gear anddriven by the transmission shaft to drive the wheels to rotate. When themotor shaft actively rotates, the transmission shaft drives the firsttransmission gear to rotate so as to rotate the wheels and the wheelsexert a force, whose direction is opposite to the rotation direction ofthe first transmission gear, to the driving member.

In one or more examples, the wheels form a second wheel gear or a secondwheel gear is mounted on the wheels. The walk-behind machine furtherincludes a second transmission gear meshing with the second wheel gear.When the wheels rotate, the first transmission gear and the secondtransmission gear rotate in opposite directions and the secondtransmission gear exerts a force, whose direction is opposite to therotation direction of the first transmission gear, to the drivingmember.

In one or more examples, the walk-behind machine further includes afriction plate disposed between the second transmission gear and thedriving member to realize the friction transmission between the secondtransmission gear and the driving member.

In one or more examples, the walk-behind machine has a self-propelledforward mode and a self-propelled backward mode. When the walk-behindmachine is in the self-propelled forward mode, the motor drives thewheels to rotate in the first direction. When the motor is turned off,the walk-behind machine is out of the self-propelled forward mode andthe walk-behind machine is pushed forward to make the wheels rotate inthe first direction, the wheels drive the movable member to move fromthe locked position to the unlocked position and the clutch gets intothe unlocked state. When the walk-behind machine is in theself-propelled backward mode, the motor drives the wheels to rotate inthe second direction opposite to the first direction. When the motor isturned off, the walk-behind machine is out of the self-propelledbackward mode and the walk-behind machine is pushed backward to make thewheels rotate in the second direction, the wheels drive the movablemember to move from the locked position to the unlocked position and theclutch gets into the unlocked state.

In one or more examples, when the motor is turned off, the walk-behindmachine is out of the self-propelled forward-moving mode and thewalk-behind machine is pushed backward to make the wheels rotate in thesecond direction, the wheels drive the movable member to move from thelocked position to the unlocked position and the clutch turns into theunlocked state. When the motor is turned off, the walk-behind machine isout of the self-propelled backward-moving mode and the walk-behindmachine is pushed forward to make the wheels rotate in the firstdirection, the wheels drive the movable member to move from the lockedposition to the unlocked position and the clutch turns into the unlockedstate.

In one or more examples, the walk-behind machine has a self-propelledforward-moving mode in which the motor drives the wheels to rotate inthe first direction and a self-propelled backward-moving mode in whichthe motor drives the wheels to rotate in the second direction oppositeto the first direction. When the motor is turned off, the walk-behindmachine could be pushed to drive the wheels to turn at an angle in anydirection and the wheels drive the movable member to move from thelocked position to the unlocked position, the clutch turning into theunlocked state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example walk-behind machine of thepresent disclosure.

FIG. 2 is a schematic view of a chassis, a motor, a transmissionmechanism and a plurality of wheels of the walk-behind machine of FIG. 1.

FIG. 3 is a schematic view of the transmission mechanism separated fromthe chassis of FIG. 2 .

FIG. 4 is a schematic view of an example motor protection shield locatedin a motor receiving slot of FIG. 2 .

FIG. 5 is a schematic view of an example anti-wrap and an examplegearbox of FIG. 4 .

FIG. 6 is a schematic view of the motor protection shield of thewalk-behind machine of FIG. 1 .

FIG. 7 is a schematic view of another perspective of the structure ofFIG. 6 .

FIG. 8 is a cross-sectional view of the structure of FIG. 6 .

FIG. 9 is an exploded view of the structure of FIG. 6 .

FIG. 10 is a schematic view showing the internal structure of thegearbox of the walk-behind machine of FIG. 1 .

FIG. 11 is a schematic view of the motor, the transmission mechanism andthe plurality of wheels of the walk-behind machine of FIG. 1 .

FIG. 12 is a schematic view of the structure of FIG. 11 after removing awheel cover.

FIG. 13 is a schematic view showing an example first transmission gearand an example second transmission gear of the transmission mechanism ofFIG. 12 respectively engaged with a first wheel gear and a second wheelgear.

FIG. 14 is a schematic view of the transmission mechanism of FIG. 13 .

FIG. 15 is a cross-sectional view of the transmission mechanism of FIG.14 .

FIG. 16 is an exploded view of the transmission mechanism of FIG. 14 .

FIG. 17 is an exploded view of another perspective of the transmissionmechanism of FIG. 14 .

FIG. 18 is a schematic view of the first transmission gear, an outerring member and a driving member of the transmission mechanism of FIG.14 .

FIG. 19 is a plan view of another perspective of the structure of FIG.18 .

FIG. 20 is a cross-sectional view of the structure of FIG. 18 along lineA-A.

FIG. 21 is a cross-sectional view of the structure of FIG. 18 along lineB-B.

FIG. 22 is a schematic view of the movable member of FIG. 20 in anunlocked position.

FIG. 23 is a schematic view of the outer ring member, a plurality ofmagnets and a spacer of FIG. 16 .

FIG. 24 is an exploded view of the structure of FIG. 23 .

FIG. 25 is a schematic view of another power tool.

FIG. 26 is a schematic illustration of a transmission shaft, the outerring member, a plurality of pins and the plurality of magnets of thepower tool of FIG. 25 .

DETAILED DESCRIPTION

As shown in FIG. 1 through FIG. 3 , a walk-behind machine 100 includes achassis 10, a handle 20, a plurality of wheels 30, a first motor 40, anda transmission mechanism 50. The walk-behind machine 100 may also becalled a power tool.

The chassis 10 is used to mount the first motor 40. The plurality ofwheels 30 are used to support the chassis 10. As the plurality of wheels30 contact the ground and rotate around a first axis 102 relative to thechassis 10, the walk-behind machine 100 rotate relative to the ground.The handle 20 is coupled to the chassis 10. Users can push the handle 20to move the chassis 10 relative to the ground, thereby moving thewalk-behind machine 100 relative to the ground. Users can control thewalk-behind machine 100 by manipulating the handle 20.

The first motor 40 includes a motor shaft 41. The first motor 40 iscapable of driving the plurality of wheels 30 to rotate. The motor shaft41 is used for outputting a driving force to the plurality of wheels 30.The motor shaft 41 rotates around a rotation axis 103 which is parallelto the first axis 102. The motor shaft 41 drives the plurality of wheels30 to rotate. In the illustrated example, the first motor 40 is anelectronic motor and the motor shaft 41 is an electronic motor shaft.The first motor 40 may also be called a self-propelling motor. Thewalk-behind machine 100 also includes a battery pack that powers thefirst motor 40. As an alternative example, the first motor 40 may alsobe an internal combustion engine powered by fuel combustion.

The transmission mechanism 50 transmits power between the first motor 40and the plurality of wheels 30. The transmission mechanism 50 connectsthe motor shaft 41 and the plurality of wheels 30 and transmits motionbetween the motor shaft 41 and the plurality of wheels 30.

The transmission mechanism 50 transfers motion in one-way between themotor shaft 41 and the plurality of wheels 30. The transmissionmechanism 50 drives the plurality of wheels 30 to rotate as the motorshaft 41 actively rotates. The transmission mechanism 50 includes aclutch 50 a. The clutch 50 a has a drive state and an unlocked state. Inthe driving state, the motor shaft 41 drives the plurality of wheels 30to rotate; in the unlocked state, the plurality of wheels 30 are free torotate relative to the motor shaft 41.

When the first motor 40 is in an off state, if the walk-behind machine100 is pushed to make the plurality of wheels 30 rotate by a certainangle in any direction, the clutch 50 a will turn to the unlocked state.That means the clutch 50 a can be unlocked when the walk-behind machine100 is pushed forward or backward to rotate the plurality of wheels 30clockwise or counterclockwise.

The transmission mechanism 50 can realize the “unlocking” by rotatingthe plurality of wheels 30 in any direction, thus it is convenient andquick for operation.

The walk-behind machine 100 has a self-driving forward mode and aself-driving backward mode. In the self-driving forward mode, therotation speed of the plurality of wheels 30 is greater than that of theplurality of wheels 30 in the self-driving backward mode.

As an alternative example, the walk-behind machine 100 includes twostart switches for respectively activating the self-driving forward modeand the self-driving backward mode.

As another alternative example, the walk-behind machine 100 includes aswitch that switches between the self-driving forward mode and theself-driving backward mode.

The walk-behind machine 100 has a manually-pushing state and aself-driving state. The walk-behind machine 100 can be convenientlymanually pushed forward or backward in the manually-pushing state and bepropelled to move by a motor instead of manual pushing force in theself-driving state.

As an alternative example, the walk-behind machine 100 turns into theself-driving forward mode when pushed forward and turns into theself-driving backward mode when pushed backward. As an alternativeexample, the walk-behind machine 100 is provided with a switch thatswitches between the manually-pushing state and the self-driving state.

In the self-driving forward mode, the first motor 40 drives theplurality of wheels 30 to rotate in the first direction and in theself-drive back mode, drives the plurality of wheels 30 to rotate in thesecond direction opposite to the first direction.

When the first motor 40 is turned off to make the walk-behind machine100 exit the self-driving forward mode and the walk-behind machine 100is pushed forward to rotate the plurality of wheels 30 in the firstdirection, the clutch 50 a turns into the unlocked state. Thewalk-behind machine 100 can enter the manually-pushing stateautomatically, not by users' additional operations such as operating anunlock trigger or unlocking switch to unlock the clutch 50 a.

When the self-propelling motor is turned off to make the walk-behindmachine 100 exit the self-driving backward mode and the walk-behindmachine 100 is pushed backward to rotate the plurality of wheels 30 inthe second direction, the clutch 50 a turns into the unlocked state. Thewalk-behind machine 100 can enter the manually-pushing stateautomatically, not by users' additional operations such as operating anunlock trigger or unlocking switch to unlock the clutch 50 a. Theself-propelling motor is turned off to make the walk-behind machine 100exit the self-driving forward mode which means the self-propelling motordoes not continue to drive the plurality of wheels 30 to rotate in thefirst direction. The self-propelling motor is turned off to make thewalk-behind machine 100 exit the self-driving backward mode which meansthe self-propelling motor does not continue to drive the plurality ofwheels 30 to rotate in the second direction.

After the first motor 40 is turned on, the walk-behind machine 100 canenter the self-driving state and can also easily switch between themanually-pushing state and the self-driving state.

When the first motor 40 is turned off to make the walk-behind machine100 exit the self-driving forward mode, the walk-behind machine 100 ispushed backward to rotate the plurality of wheels 30 in the seconddirection and the clutch 50 a turns into the unlocked state. When thefirst motor 40 is turned off to make the walk-behind machine 100 exitthe self-driving backward mode, the walk-behind machine 100 is pushedforward to rotate the plurality of wheels 30 in the first direction andthe clutch 50 a turns into the unlocked state

When the walk-behind machine 100 exits the self-driving forward mode,the first motor 40 is turned off. The clutch 50 a can turn into theunlocked state when the walk-behind machine 100 is pushed to drive theplurality of wheels 30 to rotate in any direction. That is, the clutch50 a can turn into the unlocked state when the walk-behind machine 100is pushed forward or backward to drive the plurality of wheels 30 torotate in the first or second direction.

When the walk-behind machine 100 exits the self-driving backward mode,the first motor 40 is turned off. The clutch 50 a can turn into theunlocked state when the walk-behind machine 100 is pushed to drive theplurality of wheels 30 to rotate in any direction. That is, the clutch50 a can turn into the unlocked state when the walk-behind machine 100is pushed forward or backward to drive the plurality of wheels 30 torotate in the first or second direction.

The walk-behind machine 100 includes a working element 70. The workingelement 70 is used to perform the functions of the walk-behind machine100. In the illustrated example, the working element 70 is a mowingblade and the walk-behind machine 100 is a lawn mower. The chassis 10forms a cutting cavity 11. The mowing blade rotates within the cuttingcavity 11. As another example, the working element 70 is an auger andthe walk-behind machine 100 is a snow thrower.

In the illustrated example, the working element 70 and the plurality ofwheels 30 are respectively driven by different motors. The walk-behindmachine 100 includes a second motor 60, and the second motor 60 ismounted to the chassis 10. The second motor 60 drives the workingelement 70. The second motor 60 may be an internal combustion enginepowered by fuel combustion or a motor powered by electricity. In thisexample, the second motor 60 is an electronic motor. The battery packsupplies power to the second motor 60 and the first motor 40. As shownin FIG. 1 , the walk-behind machine 100 includes a power trigger 61 anda drive trigger 42. The power trigger 61 is used to activate the secondmotor 60 and the drive the trigger 42 is used to activate the firstmotor 40. The walk-behind machine 100 may be a lawn mower and the secondmotor 60 can be called a mowing motor which drives the mowing blade torotate. When the mowing motor is powered by electricity, the mowingmotor can also be called a mowing electric motor.

As an alternative example, the working element and the wheels can bedriven by the same motor. That is, a motor, such as the first motor 40,drives the working element and also drives the wheels.

As shown in FIG. 11 to FIG. 13 , a first wheel gear 31 is mounted andfixed to the plurality of wheels 30. The first wheel gear 31 is fixedlycoupled to the plurality of wheels 30 to drive the plurality of wheels30 to rotate. A second wheel gear 32 is mounted and fixed to theplurality of wheels 30. The first wheel gear 31 and second wheel gear 32rotate in synchronization with the plurality of wheels 30. Thewalk-behind machine 100 also includes a wheel cover 33. The plurality ofwheels 30 form a cavity in which the first wheel gear 31 and the secondwheel gear 32 are located. The cavity is provided with an opening whichis covered by the wheel cover 33 to prevent dust from entering thecavity to contaminate the first wheel gear 31 and the second wheel gear32.

As another example, the first wheel gear may also be a part of thewheels, that is to say, be formed with the wheels. The second wheel gearmay also be a part of the wheels, that is to say, be formed with thewheels.

The transmission mechanism 50 includes the clutch 50 a and a gearbox 80.As shown in FIG. 12 to FIG. 17 , the clutch 50 a includes a transmissionshaft 51, a movable member 52, a driving member 53, and an outer ringmember 56.

The transmission shaft 51 is driven to rotate by the motor shaft 41 andthen drives the plurality of wheels 30 to rotate. The gearbox 80connects the transmission shaft 51 and the motor shaft 41 to make themotor shaft 41 drive the transmission shaft 51 to rotate and therotation speed of the transmission shaft 51 is lower than the rotationspeed of the motor shaft 41. As shown in FIG. 9 and FIG. 10 , thegearbox 80 includes a first driving gear 81, a first driven gear 82, asecond driving gear 83, a second driven gear 84, and an outer housing85. The first driving gear 81 is fixed to the motor shaft 41. The firstdriven gear 82 meshes with the first driving gear 81. The first drivengear 82 and the second driving gear 83 rotate coaxially. The seconddriving gear 83 and the second driven gear 84 mesh with each other. Thesecond driven gear 84 is fixed to the transmission shaft 51.

As shown in FIGS. 12-19 , the transmission mechanism 50 further includesa first transmission gear 54, a second transmission gear 55, a fixingmember 57, a friction member 58, and an elastic member 59.

The first transmission gear 54 meshes with and rotates insynchronization with the first wheel gear 31. When the first motor 40 isworking or the motor shaft 41 rotates actively, the transmission shaft51 is driven to rotate and then drives the first transmission gear 54 torotate, which further drives the plurality of wheels 30 to rotate. Thesecond transmission gear 55 meshes with and rotates in synchronizationwith the second wheel gear 32. When the plurality of wheels 30 rotate,the first transmission gear 54 and the second transmission gear 55rotate in opposite directions, and the second transmission gear 55exerts a force opposite to the rotation direction of the firsttransmission gear 54 to the driving member 53.

In the illustrated example, the first wheel gear 31 is an external gear,the second wheel gear 32 is an internal gear, the first transmissiongear 54 is an external gear, and the second transmission gear 55 is anexternal gear. The transmission shaft 51 rotates about a central axis101. The rotation axis 103 of the motor shaft is parallel to the centralaxis 101. The central axis 101 is parallel or coincident with the firstaxis 102. The first transmission gear 54 and the second transfer gear 55rotate about the central axis 101. The rotational axis of the firsttransmission gear 54 coincides with the rotational axis of the secondtransmission gear 55 so that the transmission mechanism 50 is compact.

The movable member 52 is movable between a locked position and anunlocked position relative to the transmission shaft 51. The movablemember 52 may be pins. The movable member 52 in FIG. 20 is in the lockedposition. The movable member 52 in FIG. 22 is in the unlocked position.The transmission shaft 51 drives the plurality of wheels 30 to rotatewhen the movable member 52 is in the locked position. The plurality ofwheels 30 are free to rotate relative to the transmission shaft 51 whenthe movable member 52 is in the unlocked position, that is, thetransmission shaft 51 is not driven to rotate whether the plurality ofwheels 30 rotate clockwise or counterclockwise.

The driving member 53 is driven by the plurality of wheels 30 to makethe movable member 52 move between the locked position and the unlockedposition. The driving member 53 is driven by the plurality of wheels 30to drive the movable member 52 to move from the locked position to theunlocked position.

As an example, when the plurality of wheels 30 rotate, the secondtransmission gear 55 is driven to rotate by the second wheel gear 32.The transmission between the second transmission gear 55 and the drivingmember 53 is a friction transmission such that the second transmissiongear 55 drives the driving member 53 to move to make the movable member52 move between the locked position and the unlocked position.

The transmission between the plurality of wheels 30 and the drivingmember 53 is a friction transmission. The plurality of wheels 30 exert aforce opposite to the rotation direction of the first transmission gear54 to the driving member 53. The friction member 58, realizing thefriction transmission between the plurality of wheels 30 and the drivingmember 53, is disposed between the second transmission gear 55 and thedriving member 53. The elastic member 59 exerts a force to the secondtransmission gear 55 to cause the driving member 53 and the secondtransmission gear 55 to clamp the friction member 58. The driving member53 includes a friction portion 532 which is in contact with the frictionmember 58 to transmit a frictional force.

As an alternative example, the second wheel gear, the secondtransmission gear and the friction member may not be removed and thewheels contact the driving member directly and exert a force opposite tothe rotation direction of the first transmission gear to the drivingmember directly to realize the friction transmission between them.

In the illustrated example, the fixing member 57 is coupled to androtates in synchronization with the transmission shaft 51. The fixingmember 57 forms a driving surface 571. The fixing member 57 isseparately provided to help mount and remove the transmission mechanism50. As another alternative example, the transmission mechanism may alsobe provided without a fixing member, and the driving surface, as part ofthe transmission shaft, is formed with the transmission shaft.

The outer ring member 56 is sleeved on the transmission shaft 51. Theouter ring member 56 forms a mounting groove 561 which accommodates thefixing member 57 and the movable member 52. The movable member 52 arepins. A plurality of pins is disposed in the mounting groove 561. Thenumber of the driving surfaces is the same as in number as that of thepins. The pins are located between the groove wall 562, an annularsurface, of the mounting groove 561 and the transmission shaft 51.

In the illustrated example, as shown in FIG. 16 , FIG. 17 , FIG. 23 andFIG. 24 , the power tool includes magnets 52 a. The magnets 52 a exert amagnetic attractive force to the movable member 52. The magnets 52 aexert an attractive force in the direction of the central axis 101 tothe pins.

The magnets 52 a reduce the noise generated during the moving of themovable member 52. The magnets 52 a make the movable member 52 lesslikely to topple or deflect during the movement to prevent the clutch 50a from being accidentally locked, keeping transmission reliable.

The number of magnets 52 a is equivalent to the number of pins. Aplurality of magnets 52 a are evenly distributed in the circumferentialdirection of the central axis 101.

During the movement of the pins, each pin is subjected to the same forceof the magnets, which keeps the transmission reliable. As anotheralternative example, the magnets may be annular.

The power tool also includes spacer 52 b. The spacer 52 b is locatedbetween the pins and the magnets 52 a and disposed in the mountinggroove 561. The spacer 52 b enables the pin to move smoothly within themounting groove 561. One end of the pin is in contact with the spacer 52b. The outer ring member 56 forms recesses 52 c in which the magnets 52a are disposed.

As an alternative example, the outer ring member is located between thepins and the magnets in the direction of the central axis. That is, themagnets are disposed outside the mounting groove. As an example, asshown in FIG. 25 and FIG. 26 , the power tool 200 includes a motor 201,a housing 202, and a work head 203. The motor 201 drives the workinghead 203 to rotate. The working head 203 is used to mount a workingelement. The housing 202 forms a handle 204 for users to hold. The powertool 200 includes a clutch. The clutch includes a transmission shaft205, a driving member 206, an outer ring member 207, pins 208, andmagnets 209. The driving member 206 includes a plurality of drivingportions 2061. The driving member 206, the outer ring member 207 and thepins 208 respectively have the same structure and the same mounting waywith the driving member, the outer ring member and the pins of the powertool shown in FIG. 1 to FIG. 24 . The power tools in FIG. 25 and FIG. 26are hammer and drill tools. The clutch is also called a shaft-lockstructure. The clutch of FIG. 25 and FIG. 26 differs from the clutch ofFIG. 1 to FIG. 24 in structure and in the mounting way of the magnets.The magnets 209 may be annular and surround the transmission shaft 51.The magnets 209 are located outside the mounting groove and are fixed tothe outer ring member 207. The outer ring member 207 is located betweenthe pins and the magnets 209.

The first transmission gear 54 is mounted to the outer ring member 56,and the outer ring member 56 drives the first transmission gear 54 torotate. The movable member 52 is disposed between the driving surface571 and the groove wall 562 of the mounting groove 561. The drivingmember 53 includes a plurality of driving portions 531. The drivingportions 531 get into the mounting groove 561 and contact with themovable member 52 to push the movable member 52 to move. A plurality ofdriving portions 531 and a plurality of pins are alternatively arranged.

As shown in FIG. 20 , the movable member 52 is in the locked position.The movable member 52 is simultaneously in contact with the groove wall562 and the driving surface 571 of the mounting groove 561.

At this time, the first motor 40 is working and the motor shaft 41actively rotates. When the transmission shaft 51 rotates in a clockwisedirection (the direction indicated by the arrow), the driving surface571 drives the movable member 52 to rotate in the clockwise directionfor driving the outer ring member 56 and the first transmission gear 54to rotate in the clockwise direction, thereby driving the plurality ofwheels 30 to rotate.

As shown in FIG. 18 to FIG. 21 , the movable member 52 is located at alocked position capable of simultaneously contacting the driving surface571 and the groove wall 562 of the mounting groove 561.

When the first motor 40 is working, the motor shaft 41 actively rotates,and at this time, the transmission shaft 51 rotates in a clockwisedirection (the direction indicated by the arrow). The movable member 52simultaneously contacts the groove wall 562 of the mounting groove 561and the driving surface 571. Thereby, the driving shaft 51 drives theouter ring member 56 to rotate clockwise.

The first transmission gear 54 is sleeved on the outer ring member 56.The transmission between the first transmission gear 54 and the outerring member 56 is realized through a flat portion. The clockwiserotation of the outer ring member 56 causes the first transmission gear54 to rotate clockwise. The first transmission gear 54 meshes with thefirst wheel gear 31 to drive the plurality of wheels 30 to rotate.

When the plurality of wheels 30 rotate, the driving member 53 receives aforce, opposite to the rotation direction of the first transmission gear54, from the plurality of wheels 30. That is, the driving member 53receives a force in a counterclockwise direction and is driven to theposition shown in FIG. 20 by the plurality of wheels 30. At this time,the driving member 53 blocks the movement of the movable member 52, sothat the movable member 52 cannot move from the locked position to theunlocked position, or the movable member 52 keeps in the lockedposition. The rotation of the plurality of wheels 30 drives the secondtransmission gear 55 to rotate counterclockwise. That is, the pluralityof wheels 30 drives the second transmission gear 55 to rotate in adirection opposite to the rotation direction of the first transmissiongear 54. The transmission between the second transmission gear 55 andthe driving member 53 are friction transmission. The second transmissiongear 55 exerts a force to the driving member 53 in a direction oppositeto the rotation direction of the first transmission gear 54, and thedriving member 53 is in the way of the movable member 52 from the lockedposition to the unlocked position. The driving member 53 is driven torotate to the position shown in FIG. 20 by the plurality of wheels 30.

When the movable member 52 is in the locked position and the clutch 50 ais in the locked state, and the motor shaft 41 can drive the pluralityof wheels 30 to rotate in the first direction to advance the machine. Atthis time, the walk-behind machine 100 is in the self-driving forwardmode. When the first motor 40 is stopped, or in other words, the motorshaft 41 stops rotating and the walk-behind machine 100 was draggedbackward, the plurality of wheels 30 actively rotate in a seconddirection opposite to the first direction and drive the firsttransmission gear 54 to rotate counterclockwise. The second transmissiongear 55 rotates clockwise. The force exerted by the plurality of wheels30 on the movable member 52 causes the movable member 52 to move fromthe locked position to the unlocked position. Further, the plurality ofwheels 30 can drive the driving member 53 to move, then the drivingmember 53 drives the movable member 52 move from the locked position tothe unlocked position. The plurality of wheels 30 exert a clockwiseforce to the driving member 53. The transmission between the drivingmember 53 and the transmission shaft 51 is realized with a flat shaftportion engaging in a flat hole. When the transmission shaft 51 stopsrotating, the driving member 53 can rotate relative to the transmissionshaft 51. At this time, the driving member 53 rotates by a certain angleunder the force of the plurality of wheels 30, and pushes the movablemember 52 to move from the locked position to the unlocked position.

When the first motor 40 stops working, the walk-behind machine 100 ispushed forward and the plurality of wheels 30 actively rotate, theplurality of wheels 30 drive the first transmission gear 54 to rotateclockwise. The first transmission gear 54 drives the outer ring member56 to rotate clockwise. The outer ring member 56 rotates clockwiserelative to the transmission shaft 51 to disengage the movable member 52from the locked position. The driving member 53 can block the movablemember 52 from entering the locked position on the other side. At thistime, the movable member 52 cannot simultaneously contact the groovewall 562 of the mounting groove 561 and the driving surface 571. Theouter ring member 56 is rotatable relative to the transmission shaft 51.That is, the plurality of wheels 30 are rotatable relative to thetransmission shaft.

As an alternative example, the first motor 40 has a forward rotationmode and a reverse rotation mode. In the forward rotation mode, themotor shaft 41 rotates in the first direction; in the reverse mode, themotor shaft 41 rotates in the second direction opposite to the firstdirection. That is, the rotation directions of the motor shaft 41 areopposite in the forward rotation mode and the reverse rotation mode.Furthermore, the current direction of the first motor 40 in the forwardrotation mode is opposite to that in the reverse rotation mode. Whenwalk-behind machine 100 exits the self-driving state, the motor shaft 41of the first motor 40 enters the reverse rotation mode. The rotationdirection of the motor shaft 41 is opposite to that in the self-drivingstate. The motor shaft 41 actively rotates by a certain angle to rotatethe transmission shaft 51 by a certain angle so that the movable member52 is moved from the locked position to the unlocked position to unlockthe clutch. When the walk-behind machine 100 is stopped from travelingsuddenly by a large resistance in the self-driving state and the movablemember 52 is in the locked position, there is a large static frictionbetween the movable member 52 and the outer ring member 56, that is, thelocking force of the movable member 52. When the locking force of themovable member 52 is greater than the friction between the plurality ofwheels 30 and the driving member 53, the plurality of wheels 30 cannotdrive the driving member 53 to push the movable member 52 to move fromthe locked position to the unlocked position. The reverse rotation ofthe motor shaft 41 reduces the friction between the movable member 52and the outer ring member 56 or directly moves the movable member 52 tothe unlocked position. The movable member 52 can smoothly move to theunlocked position. The walk-behind machine 100 can be pulled or pushedsmoothly.

As shown in FIG. 22 , the movable member 52 is located at an unlockedposition where the movable member 52 cannot simultaneously contact thegroove wall 562 of the mounting groove 561 and the driving surface 571.

Since the movable member 52 cannot simultaneously contact the groovewall 562 of the mounting groove 561 and the driving surface 571, thetransmission shaft 51 and the outer ring member 56 can freely rotate.That is, the transmission shaft 51 can freely rotate relative to theplurality of wheels 30. When the transmission shaft 51 stops rotating,and the plurality of wheels 30 rotate to drive the first transmissiongear 54 and the outer ring member 56 to rotate in a counterclockwisedirection (the direction indicated by the arrow), the secondtransmission gear 55 is driven to rotate clockwise by the plurality ofwheels 30. That is, the plurality of wheels 30 apply a force to thedriving member 53 opposite to the rotation direction of the firsttransmission gear 54, and the driving member 53 is driven to rotate bythe plurality of wheels 30 to the position shown in FIG. 22 . At thistime, the driving member 53 blocks the movement of the movable member52, preventing the movable member 52 from moving from the unlockedposition to the locked position, keeping the movable member 52 in theunlocked position.

The middle portion of the driving surface 571 corresponds to theunlocked position of the movable member 52, and two locked positions arerespectively on the right and left side of the unlocked position. Themovable member 52 in FIG. 20 is at the locked position on the left side.The motor shaft of the first motor 40 rotates in a direction to drivethe transmission shaft 51 to rotate in the arrow direction, so that thewalk-behind machine 100 moves forward, that is, gets into theself-driving forward mode. When the motor shaft of the first motor 40rotates in opposite direction to drive the transmission shaft 51 torotate in a direction opposite to the arrow direction, the movablemember 52 moves to the locked position on the right side, therebyrealizing the backward movement, the self-driving backward mode, of thewalk-behind machine 100.

The transmission principle and the unlocking principle of the clutch 50a are the same in the self-driving backward mode and the self-drivingforward mode.

As shown in FIG. 2 to FIG. 9 , the lawn mower includes a motor shield44. The motor shield 44 accommodates the self-propelling motor. Themotor shield 44 includes a motor guard portion 441 and a heatdissipating portion 442. The heat dissipating portion 442 protrudes fromthe motor guard portion 441 in a direction away from the ground. Themotor guard portion 441 forms a motor cavity 4411 in which theself-propelling motor is located. The heat dissipating portion 442 formsa heat dissipating cavity 4421 connected through with the motor cavity4411. The heat dissipating portion 442 is provided with heat dissipatinghole 4422 which connects the heat dissipating cavity 4421 and theoutside of the heat dissipating portion 442. The heat dissipatingportion 442 can avoid reducing the heat dissipating effect by preventingthe grass cuttings from blocking the heat dissipating holes 4422 or fromentering the motor cavity 4411.

The heat dissipating portion 442 protrudes from the motor guard portion441 in the radial direction of the rotational axis 103 of the motorshaft. The heat dissipating portion 442 is connected to one end of themotor guard portion 441 in the axial direction of the rotational axis103 of the motor shaft.

The self-propelling motor further includes a heat dissipating fan 43fixed to the motor shaft. The motor guard portion 441 forms an air hole4412; and in the axial direction of the rotation axis 103 of the motorshaft, the position of the air hole 4412 corresponds to the position ofthe heat dissipating fan 43.

The heat dissipating fan 43 rotates to drive air to flow into the motorshield 44 from the heat dissipating holes 4422 and be exhausted from theair hole 4412.

The motor shield 44 forms two heat dissipating portions 442; the heatdissipating fan 43 is located between the two heat dissipating portions442 in the axial direction of the rotational axis 103 of the motorshaft. In the axial direction of the rotational axis 103 of the motorshaft, the two heat dissipating portions 442 are respectively connectedto the two ends of the motor guard portion 441.

The motor guard portion 441 further forms an auxiliary heat dissipatinghole 4413, whose area is smaller than the area of the air hole 4412.

The heat dissipating holes 4422 are formed in a strip shape; the longlongitudinal direction of the strips coincides with the convex directionof the heat dissipating portion 442. The heat dissipating hole 4422 islocated on side wall of the heat dissipating portion 442.

The heat dissipating portion 442 forms auxiliary air hole 4423 locatedat the top end of the heat dissipating portion 442.

The lawn mower also includes an anti-wrapping sleeve 51 a which isrotatably sleeved on the transmission shaft 51. The self-propellingmotor drives the transmission shaft 51 to rotate about the central axis101.

The anti-wrapping sleeve 51 a can prevent the transmission shaft 51 frombeing entangled by the grass when it rotates.

The distance between the motor shield 44 and the anti-wrapping sleeve 51a is greater than 0 mm and less than or equal to 10 mm. The distancebetween the motor shield 44 and the anti-wrapping sleeve 51 a is greaterthan 0 mm and less than or equal to 3 mm.

The anti-wrapping sleeve 51 a is disposed at one end of the gearbox 80.The anti-wrapping sleeve 51 a and the self-propelling motor are locatedon the same side of the gearbox 80.

An annular groove 851 is formed between the outer housing 85 and thetransmission shaft 51. One end of the anti-wrapping sleeve 51 a islocated in the annular groove 851.

The anti-wrapping sleeve 51 a defines a large end 511 a and a small end511 b. The diameter of the large end 511 a is greater than that of thesmall end 511 b. The large end 511 a of the anti-wrap 51 a is closer tothe gearbox 80 than the small end 511 b. The large end 511 a of theanti-wrapping sleeve 51 a is located in the annular groove 851. Thetransmission shaft 51 extends through the gearbox 80.

The chassis 10 forms a motor housing cavity 12 in which theself-propelling motor is located. The opening of the motor housingcavity 12 coincides with that of the cutting cavity 11, and the openingof the motor housing cavity 12 is towards the ground.

In the direction of the central axis 101, the anti-wrap 51 a is locatedbetween the gearbox 80 and the wall of the motor housing cavity 12.

The basic principles, main features and advantages of the presentdisclosure are described above. Those skilled in the art shouldunderstand that the above examples do not limit the disclosure in anyway, and any technical solution of equivalent replacement or equivalenttransformation is within the protection scope of the present disclosure.

What is claimed is:
 1. A walk-behind machine comprising: a chassis; ahandle connected to the chassis; a plurality of wheels for supportingthe chassis and being rotatable relative to the chassis, wherein one ofthe plurality of wheels is a drive wheel; a motor mounted to the chassisand used for providing a driving force for rotating the drive wheel; anda transmission mechanism connecting the motor with the drive wheel,wherein the transmission mechanism comprises: a first clutch having adriving state where the motor drives the drive wheel to rotate and anunlocked state where the drive wheel is free to rotate relative to themotor, wherein, in the driving state, the motor is capable of drivingthe drive wheel to rotate in a first direction, wherein, when the motorstops rotating and the first clutch is in the driving state, the drivewheel rotates in a second direction opposite to the first direction todrive the first clutch to switch from the driving state to the unlockedstate, wherein the transmission mechanism further comprises atransmission shaft for mounting the first clutch, the drive wheel isformed with a first wheel gear and a second wheel gear, the walk-behindmachine further comprises a first transmission gear meshing with thefirst wheel gear and a second transmission gear meshing with the secondwheel gear, the first transmission gear is configured to be driven bythe transmission shaft, wherein, in the driving state, the transmissionshaft rotates to drive the first transmission gear to rotate to drivethe drive wheel to rotate, and wherein, when the motor stops rotatingand the drive wheel rotates, the first transmission gear and the secondtransmission gear rotate in opposite directions and the second wheelgear drives the second transmission gear to rotate to drive the firstclutch to switch from the driving state to the unlocked state.
 2. Thewalk-behind machine of claim 1, wherein when the first clutch is in theunlocked state, the motor is activated to rotate in the first directionto drive the first clutch to switch from the unlocked state to thedriving state.
 3. The walk-behind machine of claim 1, wherein when thefirst clutch is in the unlocked state, the motor is activated to rotatein the second direction to drive the first clutch to switch from theunlocked state to the driving state.
 4. The walk-behind machine of claim1, wherein the transmission mechanism further comprises: a gearboxconnecting the motor with the drive wheel.
 5. The walk-behind machine ofclaim 1, wherein the plurality of wheels comprises two front wheels andtwo rear wheels and the drive wheel is one of the two rear wheels, thetransmission mechanism further comprises a second clutch, the firstclutch is coupled to the drive wheel, and the second clutch is coupledto the other of the two rear wheels.
 6. The walk-behind machine of claim1, wherein the plurality of wheels comprises a first wheel and a secondwheel and the drive wheel is the first wheel, the transmission mechanismfurther comprises a second clutch, the first clutch is coupled to thefirst drive wheel, and the second clutch is coupled to the second wheel.7. The walk-behind machine of claim 6, wherein the transmission shaftmounts the first clutch and the second clutch, the first clutch ismounted at one end of the transmission shaft, and the second clutch ismounted at the other end of the transmission shaft.
 8. The walk-behindmachine of claim 1, further comprising: a mowing blade for mowing grass,wherein the mowing blade is mounted to the chassis and is rotatablerelative to the chassis.
 9. The walk-behind machine of claim 1, furthercomprising: an auger for clearing snow, wherein the auger is mounted tothe chassis and is rotatable relative to the chassis.
 10. Thewalk-behind machine of claim 1, wherein the first clutch comprises: amovable member capable of moving between a locked position in which thefirst clutch is in the driving state and an unlocked position in whichthe first clutch is in the unlocked state; a driving member for drivingthe movable member to move; a fixing member coupled to the transmissionshaft or as a part of the transmission shaft and forming a drivingsurface capable of driving the movable member; and an outer ring membersleeved on the transmission shaft, connected to the drive wheel to drivethe drive wheel to rotate and forming a mounting groove, wherein themovable member is located between a wall of the mounting groove and thedriving surface, and wherein when the motor stops rotating and the firstclutch is in the driving state, the drive wheel rotates in the seconddirection opposite to the first direction to drive the driving member torotate such that the driving member drives the movable member to move tothe unlocked position.
 11. A walk-behind machine comprising: a chassis;a handle connected to the chassis; a plurality of wheels for supportingthe chassis and being rotatable relative to the chassis, wherein one ofthe plurality of wheels is a drive wheel; a motor mounted to the chassisand used for providing a driving force for rotating the drive wheel; anda transmission mechanism connecting the motor with the drive wheel,wherein the transmission mechanism comprises: a first clutch having adriving state where the motor drives the drive wheel to rotate and anunlocked state where the drive wheel is free to rotate relative to themotor, wherein, in the driving state, the motor is capable of drivingthe drive wheel to rotate in a first direction, wherein, when the motorstops rotating and the first clutch is in the driving state, the drivewheel rotates in a second direction opposite to the first direction todrive the first clutch to switch from the driving state to the unlockedstate, a first transmission gear mounted to an outer ring member, atransmission between the first transmission gear and the outer ringmember is realized through a flat portion, the first transmission gearallowing the outer ring member to rotate relative to it within apredetermined angle, and a second transmission gear is mounted on thetransmission mechanism, and the second transmission gear drives thedrive wheel to rotate by friction.
 12. A walk-behind machine comprising:a chassis; a handle connected to the chassis a plurality of wheels forsupporting the chassis and being rotatable relative to the chassis,wherein one of the plurality of wheels is a drive wheel; a motor mountedto the chassis and used for providing a driving force for the drivewheel; and a transmission mechanism for transmitting a power output fromthe motor to the drive wheel, wherein the transmission mechanismcomprises: a clutch having a driving state where the motor is capable ofdriving the drive wheel to rotate and an unlocked state where the drivewheel is free to rotate relative to the motor, wherein, in the drivingstate, the motor is capable of driving the drive wheel to rotate in afirst direction, wherein, when the motor stops rotating and the clutchis in the driving state, the drive wheel rotates in the first directionto drive the clutch to switch from the driving state to the unlockedstate, wherein the transmission mechanism further comprises atransmission shaft for mounting the clutch, the drive wheel is formedwith a first wheel gear and a second wheel gear, the walk-behind machinefurther comprises a first transmission gear meshing with the first wheelgear and a second transmission gear meshing with the second wheel gear,the first transmission gear is configured to be driven by thetransmission shaft, wherein, in the driving state, the transmissionshaft rotates to drive the first transmission gear to rotate to drivethe drive wheel to rotate, and wherein, when the motor stops rotatingand the drive wheel rotates, the first transmission gear and the secondtransmission gear rotate in opposite directions and the second wheelgear drives the second transmission gear to rotate to drive the clutchto switch from the driving state to the unlocked state.
 13. Thewalk-behind machine of claim 12, wherein when the clutch is in theunlocked state, the motor is activated to rotate in the first directionto drive the clutch to switch from the unlocked state to the drivingstate.
 14. The walk-behind machine of claim 12, wherein when the clutchis in the unlocked state, the motor is activated to rotate in a seconddirection to drive the clutch to switch from the unlocked state to thedriving state.
 15. The walk-behind machine of claim 12, wherein thetransmission mechanism further comprises: a gearbox connecting the motorwith the drive wheel.
 16. The walk-behind machine of claim 12, whereinthe plurality of wheels comprises two front wheels and two rear wheelsand the drive wheel is one of the two rear wheels, the transmissionmechanism further comprises a second clutch, the clutch is coupled tothe drive wheel, and the second clutch is coupled to the other of thetwo rear wheels.
 17. The walk-behind machine of claim 12, wherein theplurality of wheels comprises a first wheel and a second wheel and thedrive wheel is the first wheel, the transmission mechanism furthercomprises a second clutch, the clutch is coupled to the drive wheel, andthe second clutch is coupled to the second wheel.
 18. The walk-behindmachine of claim 17, wherein the transmission shaft mounts the clutchand the second clutch, the clutch is mounted at one end of thetransmission shaft, and the second clutch is mounted at the other end ofthe transmission shaft.
 19. The walk-behind machine of claim 12, furthercomprising: a mowing blade for mowing grass, wherein the mowing blade ismounted to the chassis and is rotatable relative to the chassis.
 20. Thewalk-behind machine of claim 12, further comprising: an auger forclearing snow, wherein the auger is mounted to the chassis and isrotatable relative to the chassis.